Plasma television and power supply control device

ABSTRACT

A microcomputer  60  takes in voltages output from the sustaining voltage Vsus generation circuit  52 , the addressing voltage Vadd generation circuit  53 , and the standby voltage generating circuit  54  via A/D input ports  1  through  6  mounted on the microcomputer board, and performs examinations to judge whether abnormal values are detected about the voltages. If there is at least one abnormal value detected, the main power supply is set OFF and after a predetermined time the main power supply is set ON again to perform a reexamination. If the number of times when abnormal values about a certain voltage are detected reaches the number of abnormal value detections N, the main power supply is left OFF. The number of abnormal value detections N for the Vsamp, the Vset, the Ve or the Vscan, is set larger than the number of abnormal value detections set for the Vsus or the Vadd.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is related to the Japanese Patent Application No. 2005-372259, filed Dec. 26, 2005, the entire disclosure of which is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a plasma television and a power supply control device.

(2) Description of the Related Art

As one conventional art to protect a television receiver, the protection method of a television receiver to prohibit the main power supply of a microcomputer from being set ON after the number of protection operations to set the main power supply OFF reaches the predetermined number is well known (Refer to Japanese Patent Laid-Open No. H4-79583).

In addition, a television receiver with a function that disables the stop function for setting the switching circuit OFF when noises are detected in the main body of the television receiver for a predetermined time is well known (Refer to Japan Utility Model Publication No. 3087790).

Furthermore, the method that disables a high voltage output circuit when the number of judgments that examine the duration of an abnormal state detection signal with preset time intervals reaches the predetermined number is well known (Refer to Japanese Patent Laid-Open No. H10-327372).

In above-mentioned prior arts, measures that prevent a protection target apparatus from shutting off the power supply when noises temporally flow in the apparatus are adopted.

In apparatuses, such as television sets, it is required that main power supplies be shut off to prevent abnormal voltages from flowing in a display panel and the like when the above-mentioned abnormal voltage values are detected due to malfunctions of specified circuits that constitute part of the apparatuses. On the other hand, it is not so much required that main power supplies be shut off when the abnormal voltages are detected due to temporal inflow of noises. In addition, the judgment whether the detection of abnormal voltage values is due to a real malfunction or due to simple inflow of noises can be accurately made by repeating the above-mentioned detection process.

Here, among circuits that constitute an apparatus, the malfunctions of some circuits are liable to cause the failure of the above-mentioned display panel and the like, and the malfunctions of other circuits may not directly cause the failure of the above-mentioned display panel and the like, that is, there are various circuits with different malfunction severities mixed in the apparatus.

In above-mentioned prior arts, however, attention is not paid to the different malfunction severities of various portions that constitute an apparatus.

Therefore, there is an inappropriate case where the hasty decision that a power supply should be shut off is made even though there is enough time to judge whether the detection of abnormal voltage values have been due to a real malfunction or due to simple inflow of noises or there is another inappropriate case where, as contrasted with the former case, the above-mentioned detection process is repeated many times although the situation is so urgent that the power supply should be shut off at once with the adverse effect due to a real malfunction taken into account.

BRIEF SUMMARY OF THE INVENTION

The present invention discloses the combination of a plasma television set and a power supply control device that can realize one function to prevent an apparatus from breaking down and another function to avoid unnecessary shutting off of a power supply with an appropriate balance of the both functions.

One aspect of the present invention provides a power supply control device that sets a main power supply OFF when malfunctions occur to portions targeted for examination, comprising: a detection unit that detects abnormal values of the output voltages that are obtained from portions targeted for examination when the main power supply is ON; a power switching circuit that sets the main power supply OFF when the detection unit detects at least one abnormal value about any output voltage and sets the main power supply ON again after a predetermined time; and a switching control unit that controls the power switching circuit, wherein: the number of abnormal value detections that is set for each of the output voltages and is used for making the judgment that a malfunction has occurred in the corresponding portion targeted for examination is stored in advance; and if the number of times when abnormal values about a specified output voltage are detected by the detection unit reaches the number of abnormal value detections that is set for the output voltage, the power switching circuit is prohibited from setting the main power supply ON again when the predetermined time has elapsed since the power switching circuit set the main power supply OFF.

In the above-mentioned configuration of the present invention, the detection unit and the power switching circuit repeat fundamentally the operation many times where the main power supply is set OFF when an abnormal value is detected and the main power supply is again set ON after a while. It goes without saying that the main power supply is left ON if any abnormal value is not detected.

Here, the switching control unit changes the timing when the above-mentioned repeated operation is cut depending on which output voltage is judged to be abnormal. In other words, the switching control unit decides the above-mentioned timing based on the number of abnormal value detections that is set for each of the output voltages in advance, and if the number of times when abnormal values for a specified output voltage are detected by the detection unit reaches the number of abnormal value detections set for the output voltage, the switching control unit prohibits the power switching circuit from setting the main power supply ON again after the predetermined time has elapsed since the power switching circuit set the main power supply OFF.

As mentioned above, in an aspect of the present invention, the number of abnormal value detections is set for each of the output voltages individually, and the number of abnormal value detections set for each of the output voltages is used during the repeated process where the main power supply is set OFF when an abnormal value is detected and again set ON after a predetermined time, and then the abnormal value detection is continued.

Therefore, as to the output voltages whose abnormal values may cause serious damages, the judgment that the main power supply should be left OFF can be made at the early time. In consequence, serious failures due to malfunctions of the portions targeted for examination can be prevented from occurring. On the other hand, as to the output voltages whose abnormal values may not cause serious damages at once, the judgment whether the abnormal values are due to a real malfunction or due to temporal inflow of noises can be accurately made through a plurality of abnormal value detections, resulting in the right judgment whether the main power supply should be left OFF or not.

An optional aspect of the present invention provides power supply control device, wherein: the detection unit detects abnormal values of the output voltages that are obtained from an addressing voltage generation portion, a sustaining voltage generation portion, and a standby voltage generation portion that generate voltages fed to a plasma display panel; and the numbers of abnormal value detections related to an addressing voltage output from an addressing voltage generation portion and a sustaining voltage output from an sustaining voltage generation portion that are stored in the switching control unit are set 2.

In other words, in this aspect of the present invention, these three voltage generation units are targeted for the abnormal value detection. In the case where the addressing voltage or the sustaining voltage shows an abnormal value due to a malfunction of the addressing voltage generation unit or the sustaining voltage generation unit, this has the potential to cause great damage to the plasma display. Therefore the avoidance of damage to the plasma display is given priority over the judgment whether the abnormal value is due to a malfunction or due to temporal noises, and the numbers of abnormal value detections related to an addressing voltage and a sustaining voltage are limited to 2, resulting in the early shutting off of the main power supply.

Another optional aspect of the present invention provides a power supply control device, wherein the numbers of abnormal value detections that the switching control unit stores are those related to the output voltages from the standby voltage generation unit and a specified output voltage other than the above-mentioned sustaining voltage from the sustaining voltage generation unit, and these numbers are set larger than the numbers of abnormal values detections related to the above mentioned addressing voltage and sustaining voltage.

The output voltages from the standby voltage generation unit and the specified output voltage other than the above-mentioned sustaining voltage from the sustaining voltage generation unit have the low potential to cause damage to the plasma display even if their values are abnormal. Therefore the numbers of the abnormal values detections related to these voltages are set larger and the judgment whether the abnormal values are due to malfunctions or due to temporal noises can be cautiously decided. In consequence, the false operation, where the main power supply is shut off even if there is no need to stop the main power supply because the abnormal values are due to temporal noises, can be prevented.

Another optional aspect of the present invention provides a power supply control device, wherein the detection unit obtains the voltage values that are gotten after the output voltages from the portions targeted for examination have been individually divided and stepped down.

In other words, the voltage values output from the portions targeted for examination are high, such as 176 V, so after being stepped down to lower level voltages, for example lower than 5 V, these voltages are input to the detection unit, and the detection unit makes the judgment whether the original values are abnormal values or not using these stepped down values.

Another aspect of the present invention provides A plasma television set that sets a main power supply OFF when malfunctions occur to circuits targeted for examination, comprising: a rectifier circuit that generates DC voltage by rectifying input AC voltage; an addressing voltage generation circuit that generates an addressing voltage across a secondary winding of an embedded transformer with the DC voltage applied to a primary winding of the embedded transformer and outputs the addressing voltage to a plasma display panel; a sustaining voltage generation circuit that generates a sustaining voltage and a specified examination voltage that have different voltage levels with each other using two different tapping wires from a secondary winding of another embedded transformer with the DC voltage applied to a primary winding of the embedded transformer and outputs the sustaining voltage to the plasma display and outputs the examination voltage to the outside; a standby voltage generation circuit that generates a first erasing voltage, a second erasing voltage and a scanning voltage that have different voltage levels with each other using three different tapping wires from a secondary winding of another embedded transformer with the above mentioned DC voltage applied to a primary winding of the embedded transformer and outputs the first erasing voltage, the second erasing voltage and the scanning voltage to the plasma display; a relay circuit, located in front of the rectifier circuit, that switches the state of a main power supply ON to OFF and vice versa by switching between supply of AC voltage and cutting off of AC voltage to the rectifier circuit; and a microcomputer, equipped with a plurality of A/D input ports for the addressing voltage, the sustaining voltage, the examination voltage, the first erasing voltage, the second erasing voltage and the scanning voltage individually, that controls the relay circuit to set the main power supply OFF if any one of the input voltages are abnormal after examining whether each input voltage is abnormal or not, and again controls the relay circuit to set the main power supply ON after 1 or 2 seconds, wherein: the microcomputer stores in advance the number of abnormal value detections that is set for each of the voltages input to A/D ports and is used for making the judgment that a malfunction has occurred in the corresponding circuit; if the number of abnormal voltage detections related to the addressing voltage or the sustaining voltage reaches 2, or if the number of abnormal voltage detections related to the examination voltage, the first erasing voltage, the second erasing voltage or the scanning voltage reaches 3, the microcomputer controls the relay circuit to set the main power supply OFF and prohibits the relay circuit from setting the main power supply ON again after the predetermined time elapsed; and the addressing voltage, the sustaining voltage, the examination voltage, the first erasing voltage, the second erasing voltage and the scanning voltage are input to the corresponding A/D ports after being individually divided and stepped down.

In other words, the above-mentioned technical ideas can bring out the above-mentioned functions and effects even to a specific product such as a plasma television.

In addition, the above-mentioned technical ideas can be comprehended as the invention of the methods to realize these ideas.

Furthermore, the above-mentioned processes can be comprehended as the invention of the programs that are executed by a computer.

As explained above, the present invention can provides one function to prevent the apparatus from breaking down due to malfunctions and another function to avoid unnecessary shutting off of the power supply with an appropriate balance of the both functions because the following measures are adopted:

-   (1) The numbers of abnormal value detections are individually     decided for the output voltages from portions (circuits) targeted     for examination with correlations between malfunctions of the     portions (circuits) targeted for examination and the failure of the     apparatus taken into account. -   (2) The above mentioned numbers of abnormal value detections are     used for the judgment whether the abnormal values output from     portions (circuits) targeted for examination are due to the     malfunctions of the above mentioned portions (circuits) targeted for     examination or due to temporal inflow of noises. In other words, if     the number of times when abnormal values for any output voltage are     detected reaches the number of abnormal value detections set for the     output voltage, the judgment that the abnormal value is due to the     malfunctions is made. -   (3) And if the judgment that the abnormal values are due to the     malfunctions is made, the main power supply is left OFF.

These and other features, aspects, and advantages of the invention will be apparent to those skilled in the art from the following detailed description of preferred non-limiting exemplary embodiments, taken together with the drawings and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

It is to be understood that the drawings are to be used for the purposes of exemplary illustration only and not as a definition of the limits of the invention. Throughout the disclosure, the word “exemplary” is used exclusively to mean “serving as an example, instance, or illustration.” Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

Referring to the drawings in which like reference character(s) present corresponding parts throughout:

FIG. 1 is an exemplary illustration of a block diagram showing a schematic configuration of a plasma television set;

FIG. 2 is an exemplary illustration of a block diagram showing a configuration of a power supply circuit and so on;

FIG. 3 is an exemplary illustration of a drawing showing an internal structure of a sustaining voltage generation circuit; and

FIG. 4 is an exemplary illustration of a flow chart showing concrete contents of a power supply control processing.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the invention and is not intended to represent the only forms in which the present invention may be constructed and or utilized.

An embodiment of the present invention will be described in the following sequence:

-   (1) Configuration of a plasma television -   (2) Configuration of a power supply circuit and others -   (3) Concrete contents of a power supply control processing -   (4) Conclusion

(1) Configuration of Plasma Television Set

FIG. 1 is a block diagram showing a schematic configuration of a plasma television set related to the present invention.

As shown in FIG. 1, the plasma television set 100 is mainly composed of a plasma display panel (PDP for short hereafter) 40, an image processing circuit 20, a tuner circuit 10, a microcomputer 60, a panel driving circuit 30, and a power supply circuit 50. The tuner circuit 10 obtains TV broadcast waves through an antenna 10 a and extracts image signals etc. from the TV broadcast waves within the frequency bandwidth specified by the microcomputer 60. Equipped with an program executing environment composed of embedded CPU, ROM and RAM, the microcomputer 60 controls the whole behavior of the plasma television set 100. In addition, the microcomputer 60 can also perform a power supply control processing to be described later as one of its functions.

The image processing circuit 20 generates digital image signals based on image signals input by the tuner circuit 10. The digital image signals generated by the image processing circuit 20 is input to the panel driving circuit 30, and this panel driving circuit 30 generates driving signals for PDP 40 based on the digital image signals.

Through the above-mentioned configuration, images based on the TV broadcast waves can be reproduced on PDP 40. It goes without saying that the plasma television set can reproduce images from TV image signals of CATV or from image signals input by a DVD video deck and the like as well as image signals received by the antenna 10. TV broadcast waves that are input to the tuner circuit 10 can be either digital or analog as long as the image processing circuit 20 is compatible with incoming signals.

The power supply circuit 50 takes in commercial alternative voltage AC through a power cable 57 and generates a sustaining voltage Vsus, an addressing voltage Vadd, a first erasing voltage Vset, a second erasing voltage Ve, and a Scanning voltage Vscan as power supply voltages to drive PDP40. In addition, the power supply circuit 50 supplies necessary powers not only to PDP 40 but also to the microcomputer 60 and other circuits that compose the plasma television set 100.

The sustaining voltage Vsus and the addressing voltage Vadd are fed to sustaining electrodes and addressing electrodes of many cells, which PDP 40 is equipped with, respectively, while the scanning voltage Vscan is fed to scanning electrodes of the above mentioned many cells. In PDP 40 of this embodiment of the present invention, the surface discharge method is adopted, wherein discharges occurs in the direction of the display surface of the PDP 40 by applying pulse voltages to the scanning electrodes and sustaining electrodes of cells that were pre-discharged across the addressing electrodes. The fist erasing voltage Vset and the second erasing voltage Ve are used to erase electric charges that stay behind in the cells. The above-mentioned voltages are output to PDP 40 in a specific order and time sequence after the plasma display 100 is started up.

(2) Configuration of Power Supply Circuit and Others

FIG. 2 is a block diagram showing the power supply circuit 50, the microcomputer 60 and the like.

In the power supply circuit 50, a rectifier circuit 51 takes in alternative voltage AC and converts this alternative voltage AC to a direct current voltage DC with a preset level (385 V for example). Then the generated direct current voltage DC is fed to a sustaining voltage Vsus generation circuit 52, an addressing voltage Vadd generation circuit 53, and a standby voltage generation circuit 54 in parallel. These voltage generation circuits 52 through 54 have embedded transformers of their own with specific turn ratios. And after getting the direct current DC inputs to the primary windings of their own embedded transformers, these voltage generation circuits generate the sustaining voltage Vsus, the addressing voltage Vadd, the first erasing voltage Vset, the second erasing voltage Ve and the scanning voltage Vscan with desirable voltage levels across the secondary windings of the embedded transformers respectively.

FIG. 3 briefly shows an internal structure of the sustaining voltage generation circuit 52.

The direct current voltage DC output from the rectifier 51 that equipped with a rectifier bridge circuit (not shown in the figure) is applied to a terminal of a first winding of a transformer 52 a. A secondary winding of the transformer 21 has two different tapping wires, and two voltages with two different values are output from these two tapping wires. A DC voltage output from one of tapping wires with its output voltage adjusted to 176 V is the sustaining voltage Vsus, and as mentioned above this sustaining voltage Vsus is fed to PDP40.

In addition, a DC voltage output from another tapping wire with its output voltage adjusted to a preset value (−0.5 V for example) is an examination voltage Vsamp. When the direct current Voltage DC output from the rectifier circuit 51 has a stable voltage level 358 V, the examination voltage Vsamp has also a stable voltage value, that is, the preset value. But if the direct current Voltage DC has an unstable voltage value, Vsamp has also an unstable voltage value. In other words, the examination voltage Vsamp is a voltage for judging whether the rectifier circuit 51 has any malfunction or not. The examination voltage Vsamp is not fed to PDP40 but fed to the microcomputer 60 so that it is judged whether the level of the examination voltage Vsamp is normal or not as described later,

In addition, the standby voltage generation circuit 54 has also an embedded transformer, and a secondary winding of the transformer has three different tapping wires. Three voltages with different voltage levels, that is, the first erasing voltage Vset, the second voltage Ve, and the scanning voltage Vscan, are output from these three tapping wires and fed to PDP40.

Now let us get back to FIG. 2 and continue to explain the following. As shown in FIG. 2, the microcomputer 60 is equipped with a plurality of analog-to-digital converter (A/D) input ports A/D1 through A/D6 to obtain output voltages from the above-mentioned generation circuits 52 through 54.

In this embodiment of the present invention, A/D input port 1 takes in the examination voltage Vsamp, A/D input port 2 takes in the sustaining voltage Vsus, A/D input port 3 takes in the addressing voltage Vadd, A/D input port 4 takes in the first erasing voltage Vset, A/D input port 5 takes in the second erasing voltage Ve, and A/D input port 6 takes in the scanning voltage Vscan. And then these input voltages undergo A/D conversion to be input to the microcomputer 60.

In addition, output voltages from above-mentioned generation circuits 52 through 54 are not fed to A/D input ports with their voltage levels intact, but they are fed after their voltage levels are lowered by resistive voltage dividers that are not shown in the figure.

A relay circuit 55 is mounted in front of the rectifier circuit 51. Here, the microcomputer 60 outputs a switching signal from port PW1 for setting a switch of the relay circuit 55 ON or OFF in order to enable or disable a main power supply respectively. More specifically, a switching transistor Tr1 for driving a relay coil of the relay circuit 55 is mounted between the microcomputer 60 and the relay circuit 55. The microcomputer 60 applies the switching signal to the transistor. If the switching signal is high (H) level, the switch of the relay circuit 55 is set ON to enable the main power supply, and if the switching signal is low (L) level, the switch of the relay circuit 55 is set OFF to disable the main power supply. In addition, there is a resistor R1 in parallel with the above-mentioned switch in the relay circuit 55 so that an input terminal of a power switching circuit and an output terminal of the power switching circuit is connected through the resistor R1 with the result that a standby power supply voltage with a certain level is fed to the microcomputer 60 even if the above-mentioned switch is OFF. The above-mentioned standby power supply voltage is fed to the microcomputer 60 via the standby generation circuit 54.

(3) Concrete Contents of a Power Supply Control Processing

In the above-mentioned configuration, the microcomputer 60 performs the following power supply control processing. FIG. 4 is a flow chart showing concrete contents of a power supply control processing that the microcomputer 60 performs. Firstly, at Step S100 (“Step” is omitted for short hereafter. For example S100 for Step S100), the microcomputer 60 judges whether the main power supply is ON or OFF. In other words, the microcomputer 60 monitors the pushing operation of the main power supply switch by a user and the power-on instruction to the main power supply via a remote-control transmitter.

In consequence of the monitoring, if the above-mentioned pushing operation or power-on instruction is detected, the microcomputer 60 outputs the switching signal with H level from port PW1 to set the switch of the relay circuit ON, and then judges that the main power supply is ON.

After the judgment that the main power supply was ON was made, the microcomputer 60 judges whether a certain non-examination period (300 msec for example) has elapsed or not (at S110). If the non-examination period has elapsed, the microcomputer 60 examines the levels of the voltages input from A/D input ports 1 through 6 (at S120). Here the reason why the non-examination period is set is because it is necessary to wait for a while until all the output voltages from the above-mentioned generation circuits 52 through 54 have gotten stabilized after the main power supply was set ON.

In the above-mentioned examination, the microcomputer 60 judges whether the voltages input from A/D input ports 1 through 6 are within the normal ranges preset for the individual voltages or not. The microcomputer 60 stores the normal ranges for the individual voltages from A/D input ports 1 through 6. For example, if a voltage input to a certain port is within 2.5±1V, the microcomputer judges that the voltage is normal. And if the voltage is beyond this range, the microcomputer judges that the voltage is abnormal. In addition, the examination related to a voltage input to one A/D port is performed during a certain period (150 msec for example), and if at least one sample value of the voltage during this period is beyond the above-mentioned range, the microcomputer 60 judges that the voltage input to the A/D port is abnormal.

At S130, the microcomputer 60 judges whether any voltage input to A/D input ports 1 through 6 is abnormal or not. If there is an abnormal voltage values, the microcomputer 60 judges whether the abnormal value is the sustaining voltage Vsus or the addressing voltage Vadd, that is, whether the abnormal value is the voltage value obtained via A/D input port 2 or A/D input port 3. If the abnormal voltage value is the voltage value obtained via A/D input port 2 or A/D input port 3, the judgment “Yes” is made, and the flow proceeds to S150. On the other hand, the voltage value judged as abnormal belong to any one of the examination voltage Vsamp, the first erasing voltage Vset, the second erasing value Ve or the scanning voltage Vscan, that is, any one of the voltage values obtained via A/D input port 4 through 6, the judgment “No” is made, and the flow proceeds to S200.

At S120, S130, and S140, the microcomputer works as a detection unit.

Furthermore, if the judgment that there is no abnormal voltage value detected at any of the A/D input ports is made, the main power supply is left ON (at S260).

Next the processes after the flow proceeds along the “Yes” branch at the judgment of S140 will be described.

At S150, the microcomputer 60 outputs the switching signal with L level from port PW1 for setting the switch of the relay circuit 55 OFF in order to disable the main power supply.

In other words, the sustaining voltage Vsus or the addressing voltage Vadd shows an abnormal value due to some reason, the main power supply is once set OFF.

At S150, the relay circuit works as a power switching circuit and the microcomputer works as a switching control unit.

At S160, the microcomputer 60 judges whether a predetermined time (a period between 1 sec to 2 sec. This period is assumed to be 2 sec in this embodiment of the present invention.) has elapsed or not after the main power supply was set OFF. If the judgment that the predetermined time has elapsed is made, the microcomputer 60 outputs the switching signal with H level from port PW1 for setting the switch of the relay circuit 55 ON in order to enable the main power supply again at S170.

In other words, because there is a possibility the above-mentioned abnormal value occurs due to temporal inflow of noises, the main power supply is enabled again for a reexamination.

At S160 and S170, the relay circuit works as a power switching circuit and the microcomputer works as a switching control unit.

Enabling the main power supply again allows the microcomputer 60 to get ready to obtain the voltage values output from A/D input ports 1 through 6. Then at S180, the microcomputer 60 again examines the voltage levels input via A/D input ports.

Using the results of the reexamination at S180, the microcomputer 60 makes the judgment whether an abnormal value is detected about any of the input voltages from A/D input ports or not (at S190). And if an abnormal value is detected again from a certain A/D input ports from which another abnormal value has been already detected, the flow proceeds to S270.

The fact that should be taken into consideration before the examination at S180 is that an abnormal value has already detected about the sustaining voltage Vsus input from A/D input port 2 or the addressing voltage Vadd input from A/D input port 3 in the examination at S120. Therefore at S190 if an abnormal value is detected from the same input port again, the flow proceeds to S270 and the microcomputer 60 outputs the switching signal with L level from port PW1 for setting the switch of the relay circuit 55 OFF in order to disable the main power supply.

More specifically, when an abnormal value is detected about the sustaining voltage Vsus or the addressing voltage Vadd due to a malfunction of the sustaining voltage generation circuit 52 or due to a malfunction of the addressing voltage generation circuit 53, such an abnormal voltage like this continuously applied to PDP40 imposes a heavy load to PDP40, likely resulting in the failure of DPD40. Therefore in this embodiment of the present invention, if an abnormal value has been detected about the sustaining voltage Vsus or the addressing voltage Vadd twice in a row in the examinations at S120 and S180, no further examinations are performed and the main power supply is left OFF with the above-mentioned risk taken into consideration, although there is still a possibility the abnormal value temporally occurs due to inflow of noises.

At S180, S190 and S270, the microcomputer works as a detection unit and switching control unit, and the relay circuit works as a power switching circuit.

After the flow reaches S270, the main power supply is never set ON unless there is the pushing operation of the main power supply switch by a user or the power-on instruction to the main power supply via a remote-control transmitter.

On the other hand, if there is no abnormal voltage value detected from any of the A/D input ports, the microcomputer 60 leaves the main power supply ON. In other words, in the case where an abnormal value is not detected again in the examination at S180 although there has been an abnormal value detected about the sustaining voltage Vsus or the addressing voltage Vadd in the examination at S120, the judgment that the abnormal value detected at S120 is due to temporal inflow of noises is made, and the main power supply is left ON afterward.

Next the processes after the flow proceeds along the “No” branch at the judgment of S140 will be described.

The microcomputer 60 performs the same operations at S200 through S230 as at S150 through 180. The fact that should be taken into consideration before the examination at S230 is that an abnormal value has already detected about any voltage from A/D input port 1 or port 4 through 6 in the examination at S120.

Then using the results of the reexamination at S230, the microcomputer 60 makes the judgment whether an abnormal value is detected about any of the input voltages from A/D input ports or not at S240.

If an abnormal value is detected about the voltage from the same A/D port as in the former examination in a row, the flow proceeds to S250. On the other hand, if there is no abnormal voltage value detected from any of the A/D input ports, the flow proceeds to S260 and the main power supply is left ON.

At S250, the microcomputer makes the judgment whether the number of times when abnormal values for the voltage from a certain A/D input port are detected reaches the number of abnormal value detections set for the voltage in advance or not. The number of abnormal value detections N is the number of abnormal value detections that is used for making the judgment that a malfunction has occurred in a circuit for generating the voltage input to a certain A/D input port or a circuit that has an effect on generation of the voltage and the number of abnormal value detections N can be individually set for the voltage input to each A/D input port. In this embodiment of the present invention, the numbers of abnormal value detections Ns related to A/D input ports 1, and 4 through 6 are set 3 in common. And the abnormal value detection in the examination at S120 is also counted towards N.

At S250, if the judgment that the number of times when abnormal values for the voltage from any A/D input port are detected do not reach the corresponding number of abnormal value detections N is made, the flow gets back to S200, and such operations as disabling the main power supply, enabling the main power supply, and reexaminations are repeated afterwards. On the other hand, for example, if voltages input to A/D input port 1 show abnormal values three times in a row (once in the examination at S120 and twice in the reexamination at S230), the microcomputer 60 does not perform further reexaminations and the flow proceeds to S270. At S270, the microcomputer 60 outputs the switching signal with L level from port PW1 for setting the switch of the relay circuit 55 OFF in order to disable the main power supply.

In other words, if the results of the examinations related to the examination voltage Vsamp, the first erasing voltage Vset, the second erasing voltage Ve and the scanning voltage Vscan at S120 and S230 show abnormal values three times in a row about the same voltage, the microcomputer 60 sets the main power supply OFF and leaves it OFF afterward.

Even if the results of the examinations related to the examination voltage Vsamp, the first erasing voltage Vset the second erasing voltage Ve or the scanning voltage Vscan show abnormal values due to a malfunction of the rectifier circuit 51 or of the standby voltage generation circuit 54, these abnormal values do not impose a heavy load to PDP40, and it is unlikely that these abnormal values directly cause the failure of DPD40 when compared with a malfunction of the sustaining voltage Vsus generation circuit or of the addressing voltage Vadd generation circuit.

Therefore in this embodiment of the present invention, only if the results of the examinations related to the examination voltage Vsamp, the first erasing voltage Vset, the second erasing voltage Ve and the scanning voltage Vscan show abnormal values more times in a row than the results of the examinations related to the sustaining voltage Vsus and the addressing voltage Vadd, the microcomputer 60 sets the main power supply OFF and leaves it OFF afterward.

In consequence, the false operation, where the main power supply is shut off even if the abnormal values are due to temporal flow of noises, can be effectively prevented.

By the way, in the description about the case where abnormal values are detected about the sustaining voltage Vsus or the addressing voltage Vadd, the phrase “the number of abnormal value detections N” is daringly not used. But in this embodiment of the present invention, if abnormal values have been detected about the same voltage of the sustaining voltage Vsus or the addressing voltage Vadd twice in a row in the examinations at S120 and S180, the main power supply is set OFF and left OFF afterward. So the number of abnormal value detections N is equal to 2.

Therefore in a practical sense, the microcomputer 60 stores in advance the numbers of abnormal value detections Ns that are individually set for the voltages input to A/D input ports 1 through 6 in a specified memory area, and determines the number of reexaminations and judges whether a further reexamination is necessary or not with reference to the relation between each port number and the corresponding number of abnormal value detections N.

It rarely happens, but there is the case where an abnormal value is detected about a voltage from a certain A/D input port in the reexamination at S180 although an abnormal value has been detected about a voltage from another A/D input port in the previous examination (at S120) or another case where an abnormal value is detected about a voltage from a certain A/D input port in the reexamination at S230 although an abnormal value has been detected about a voltage from another A/D input port in the previous examination (at S120 or at S230). In such a case, the judgment that the number of abnormal value detections N is 1 about the voltage from the A/D input port in the last reexamination can be made.

At S200, S220, S230, S240 and S270, the microcomputer works as a detection unit and switching control unit, and the relay circuit works as a power switching circuit.

(4) Conclusion

As described above, in the present invention, the microcomputer 60 takes in a plurality of voltages output from the sustaining voltage Vsus generation circuit 52, the addressing voltage Vadd generation circuit 53, and the standby voltage generating circuit 54 via A/D input ports 1 through 6, and performs examinations to judge whether abnormal values are detected or not about the voltages taken in. If there is at least one abnormal value detected, the main power supply is set OFF and after a predetermined time, the main power supply is set ON again to perform a reexamination. And if the number of times when abnormal values for a certain voltage are detected reaches the number of abnormal value detections N set in advance, the main power supply is left OFF.

When an abnormal value about the sustaining voltage Vsus or the Addressing voltage Vadd is detected due to the malfunction of the corresponding circuit, the number of abnormal value detections N is set small in order to determine at once that the main power supply be left OFF because the malfunction of circuits corresponding to Vsus and Vadd have the potential to cause great damage to PDP40. On the other hand, as for the examination voltage Vsamp, the first erasing voltage Vset, the second erasing voltage Ve or the scanning voltage Vscan, the number of abnormal value detections N is set larger than the number set for the sustaining voltage Vsus or the Addressing voltage Vadd in order to make the judgment whether the abnormal values are due to malfunctions or due to temporal noises more cautiously because the malfunction of circuits corresponding to Vsamp, Vset, Ve and Vscan may not necessarily cause the failure of PDP40 at once.

In consequence, one function to prevent the apparatus from breaking down and another function to avoid unnecessary shutting off of the power supply can be satisfied at the same time.

Although the invention has been described in considerable detail in language specific to structural features and or method acts, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as preferred forms of implementing the claimed invention. Therefore, while exemplary illustrative embodiments of the invention have been described, numerous variations and alternative embodiments will occur to those skilled in the art. Such variations and alternate embodiments are contemplated, and can be made without departing from the spirit and scope of the invention. 

1. A plasma television set, comprising: an unit that sets a main power supply OFF when malfunctions occur to circuits targeted for examination, including: a rectifier circuit that generates DC voltage by rectifying input AC voltage; an addressing voltage generation circuit that generates an addressing voltage across a first, secondary winding of a first embedded transformer with the DC voltage applied to a first, primary winding of the first embedded transformer and outputs the addressing voltage to a plasma display panel; a sustaining voltage generation circuit that generates a sustaining voltage and a specified examination voltage that have different voltage levels from each other using two different tapping wires from a second, secondary winding of a second embedded transformer with the DC voltage applied to a second, primary winding of the second embedded transformer and outputs the sustaining voltage to the plasma display and outputs the examination voltage to the outside; a standby voltage generation circuit that generates a first erasing voltage, a second erasing voltage and a scanning voltage that have different voltage levels from each other using three different tapping wires from a third, secondary winding of a third embedded transformer with the DC voltage applied to a third primary winding of the third embedded transformer and outputs the first erasing voltage, the second erasing voltage and the scanning voltage to the plasma display; a relay circuit coupled with the rectifier circuit toggles the state of a main power supply by switching between supply of AC voltage and cutting off of AC voltage to the rectifier circuit; and a microcomputer equipped with a plurality of A/D input ports for the addressing voltage, the sustaining voltage, the examination voltage, the first erasing voltage, the second erasing voltage and the scanning voltage, individually, that controls the relay circuit to set the main power supply OFF if any one of the input voltages are abnormal after examining whether each input voltage is abnormal, and again controls the relay circuit to set the main power supply ON after 1 or 2 seconds; the microcomputer stores in advance the number of abnormal value detections that is set for each of the voltages input to A/D ports and is used for making the judgment that a malfunction has occurred in the corresponding circuit; if the number of abnormal voltage detections related to one of the addressing voltage, the sustaining voltage reaches 2, the examination voltage, the first erasing voltage, the second erasing voltage, and the scanning voltage reaches 3, the microcomputer controls the relay circuit to set the main power supply OFF and prohibits the relay circuit from setting the main power supply ON again after the predetermined time elapsed; and the addressing voltage, the sustaining voltage, the examination voltage, the first erasing voltage, the second erasing voltage and the scanning voltage are input to the corresponding A/D ports after being individually divided and stepped down.
 2. A power supply control device that sets a main power supply OFF when malfunctions occur to portions targeted for examination, comprising: a detection unit that detects abnormal values of the output voltages that are obtained from portions targeted for examination when the main power supply is ON; a power switching circuit that sets the main power supply OFF when the detection unit detects at least one abnormal value from any output voltage and sets the main power supply ON again after a predetermined time; and a switching control unit that controls the power switching circuit: the number of abnormal value detections that is set for each of the output voltages and is used for making a judgment that a malfunction has occurred in a corresponding portion targeted for examination is stored in advance; and if the number of times when abnormal values from a specified output voltage are detected by the detection unit reaches the number of abnormal value detections that is set for the output voltage, the power switching circuit is prohibited from setting the main power supply ON again when the predetermined time has elapsed since the power switching circuit set the main power supply OFF.
 3. A power supply control device according to claim 2, wherein: the detection unit detects abnormal values of the output voltages that are obtained from an addressing voltage generation portion, a sustaining voltage generation portion, and a standby voltage generation portion that generate voltages fed to a plasma display panel; and the numbers of abnormal value detections related to an addressing voltage output from an addressing voltage generation portion and a sustaining voltage output from an sustaining voltage generation portion that are stored in the switching control unit are set
 2. 4. A power supply control device according to claim 3, wherein the numbers of abnormal value detections related to output voltages output from the standby voltage generation portion and a specified output voltage output from the sustaining voltage generation portion other than the sustaining voltage are set larger than the numbers of abnormal value detections related to the addressing voltage and the sustaining voltage.
 5. A power supply control device according to claim 2, wherein the detection unit obtains the voltage values that are gotten after the output voltages from the portions targeted for examination have been individually divided and stepped down.
 6. A power supply control device according to claim 2, wherein in the second examination or thereafter, if an abnormal value is detected about a portion targeted for examination other than the portion targeted for examination where an abnormal value was detected in the previous examination by the detection unit, the detection unit continues to examine the voltage about the portion targeted for the examination where an abnormal value is detected in the second examination or thereafter until the number of times when abnormal values are detected reaches the number of abnormal value detections. 